Drilling hammer or impact hammer

ABSTRACT

A drill hammer or riveter, includes a housing ( 11 ), in which a hammering mechanism ( 12 ) is accommodated that in an axially displaceably supported guide tube ( 13 ) has a reciprocating piston ( 16 ) and a striker ( 17 ), drivable by the piston ( 16 ) via an air cushion; the hammering mechanism ( 12 ) can be moved out of an idling position into a hammering position by an axial displacement of the guide tube ( 13 ); the guide tube ( 13 ) is urged by a restoring spring ( 27 ) in the direction of the idling position with a restoring force: and between the guide tube ( 13 ) and the housing ( 11 ), at least one damping and/or spring member ( 30, 36, 37 ) is provided, which in the hammering position of the guide tuber ( 13 ) has a spring or damping characteristic between the guide tube ( 13 ) and the housing ( 11 ) that deviates from the restoring spring ( 27 ) in the region of the idling position.

PRIOR ART

The invention is based on a drill hammer or riveter as genericallydefined by the preamble to claim 1. From European Patent Disclosure EP-A429 475, a drill hammer or riveter is known which has a guide tubesupported axially displaceably in a housing. An axially reciprocatingpiston, which is coupled via an air cushion to a striker, isaccommodated in the guide tube. A restoring spring urges the guide tubewith a restoring force in the direction of a front outset position, inwhich the air cushion is ventilated via an opening in the guide tube, sothat the hammering mechanism of the drill hammer or riveter goes intothe idling mode and no further axial impacts are exerted on a tool. Ifthe guide tube is forced axially rearward out of this position by theapplication of the drill hammer or riveter against a machining pointcounter to the prestressing force of the restoring spring, then theventilation opening is closed, and the hammering mechanism enters thehammering position. In the riveting mode, via a riveting die the guidetube experiences reverse impacts, which are transmitted to the housingvia the restoring spring. To the operator of the drill hammer orriveter, these reverse impacts are irritating, so that the attempt ismade to avoid or reduce them as much as possible.

ADVANTAGES OF THE INVENTION

The drill hammer or riveter according to the invention having thecharacteristics of claim 1 has the advantage that the vibration causedby the hammering mechanism can be reduced in a relatively simple way.

By the provisions recited in the dependent claims, advantageousrefinements of and improvements to the drill hammer or riveter accordingto the invention are possible.

DRAWINGS

Three exemplary embodiments of the invention are shown in the drawingand described in further detail in the ensuing description. FIGS. 1-3each show a section through the front part of a drill hammer; in theupper half of each drawing, a half section through the drill hammer isshown in an idling position, while in the lower half of each drawing, ahalf section through the drill hammer in a hammering position is shown.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

In FIG. 1, reference numeral 10 indicates a drill hammer, which has ahousing 11 in which a hammering mechanism 12 is accommodated. Inside thehousing 11, a guide tube 13 is rotatable in bearing points 14, 15 and islimitedly displaceable axially. The guide tube, in a known manner, holdsa piston 16, a striker 17, and a riveting die 18. The piston 16 can bedriven to reciprocate via a connecting rod 19. The guide tube 13, on itsend remote from the connecting rod 19, forms a tool holder 20 to receivea tool, not shown in detail.

The riveting die 18 is provided with an encompassing collar 21, by wayof which it can be braced to the rear, toward the piston 16, via adamping ring 22 and a stop ring 23 as well as a snap ring 24 on theguide tube 13. Between the piston 16 and the striker 17, an air cushionspace 25 is formed, which can be ventilated via radial through bores 26in the guide tube 13. A restoring spring 27, which is braced toward thehousing on a bearing ring 28 solidly connected to the housing and towardthe guide tube on a disk 29, acts upon the guide tube 13 with arestoring force that is oriented forward, toward the tool holder 20.

In the upper half of FIG. 1, the drill hammer 10 is shown in an idlingposition, in which the guide tube 13 is forced into a forward outsetposition by the restoring spring 27, in the direction toward the toolholder 20. The force of the restoring spring 27 is transmitted first toa damping element 30 via the disk 29, which forms a first axial stoptoward the guide tube, and then to the guide tube 13, via a retainingdisk 31 and a securing ring 34. The retaining disk 31 forms a secondaxial stop toward the housing. Toward the front, the axial displacementof the guide tube 13 is limited by an annular disk 32, which serves thesecuring ring 34 as a front stop toward the housing. The annular disk 32is axially braced in turn on the bearing 14 via an O-ring 33.

In the idling position, the air cushion space 25 is ventilated via thethrough bores 26, so that no effective air cushion can build up betweenthe piston 16 and the striker 17, and as a result the hammeringmechanism 12 is not activated.

In the lower half of FIG. 1, the drill hammer 10 is shown in thehammering position, in which the through bores 26 are radially coveredby the bearing 15, so that the air cushion space 25 is sealed off. As aconsequence of the reciprocating motion of the piston 16, the result isaccordingly a buildup of an air cushion in the air cushion space 25, byway of which the striker 17 can likewise be driven to reciprocate. Thestriker 17 then acts upon the riveting die 18 with axial impacts, whichthe riveting die passes on to the tool, not shown in further detail, inthe tool holder 20, in the course of which the riveting die 18experiences reverse impacts, as reaction forces, from the tool in thedirection of the hammering mechanism 12. These reverse impacts aretransmitted to the guide tube 13 via the damping ring 22, stop ring 23,and snap ring 24.

The guide tube 13 is cushioned from the housing 11 at the back via therestoring spring 27. In the hammering position, however, the restoringspring 27 is compressed so far that the damping element 30, which isseparate from the restoring spring 27, is braced toward the housingdirectly on the bearing ring 28. In this way, the reverse impacts of theriveting die 18, transmitted to the guide tube 13, are absorbed by thehousing 11, bypassing the restoring spring 27, and effectively damped bythe damping element 30.

The exemplary embodiment of FIG. 2 differs from the exemplary embodimentof FIG. 1 only in that a cup spring assembly 36 is used instead of adamping element 30. All the other parts, as in the third exemplaryembodiment in FIG. 3 that follows, are identified by the same referencenumerals. Because of the cup spring assembly 36, a longer spring travelof the guide tube 13 after a reverse impact by the riveting die 18 canbe attained, compared to the damping element 30 of FIG. 1, and as aresult a damping that differs from that of the damping element 30 isattainable.

In the exemplary embodiment of FIG. 3, as the spring and/or dampingmember between the guide tube 13 and the housing 11, a helical spring 37is provided, instead of the damping element 30 of FIG. 1 and the cupspring assembly 36 of FIG. 2. With the aid of the helical spring 37, adifferent spring characteristic can be attained compared to that withcup springs. In this case as well, a reverse impact damping that isindependent from the restoring spring 27 is assured in the hammeringposition.

As an alternative to the exemplary embodiments shown, it is alsoconceivable to combine a damping element 30 with a cup spring assembly36 or with a helical spring 37 or with other damping and/or springmembers, and this can be done in either a parallel or series connection.The drill hammer 10 can also be embodied purely as a riveter, without arotational drive of the guide tube 13. The damping and/or spring member30, 36, 37, which is in addition to the restoring spring 27, can also beembodied by the restoring spring itself instead, if the restoring springhas a nonlinear spring or damping characteristic. What is essential isthat in the hammering position of the guide tube 13, the spring and/ordamping member between the guide tube 13 and the housing 11 has a springor damping characteristic that differs from the restoring spring 27 inthe region of the idling position of the guide tube.

What is claimed is:
 1. A drill hammer or riveter, comprising a housing(11) wherein a hammering mechanism (12) is accommodated in the housing,wherein, in an axially displaceably supported guide tube (13), thehammering mechanism has a reciprocating piston (16) and a striker (17),drivable by means of the piston (16) via an air cushion, wherein thehammering mechanism (12) is moveable out of an idling position into ahammering position by means of an axial displacement of the guide tube(13), wherein the guide tube (13) is urged by a restoring spring (27) ina direction of the idling position with a restoring force, whereinbetween the guide tube (13) and the housing (11), at least one dampingor spring member (30, 36, 37) is provided, wherein, in the hammeringposition of the guide tube (13), the at least one damping or springmember has either a spring or damping characteristic between the guidetube (13) and the housing (11) that deviates from the restoring spring(27) in the region of the idling position.
 2. The drill hammer orriveter or claim 1, wherein the at least one damping spring member (30,36, 37) is formed by a component embodied separately from the restoringspring (27).
 3. The drill hammer or riveter of claim 2, wherein the atleast one damping spring member (30, 36, 37), in the hammering positionof the guide tube (13), rests on a first axial stop (31), toward theguide tube, and on a second axial stop (29), toward the housing.
 4. Thedrill hammer or riveter of claim 3, wherein the restoring spring (27) isbraced on one of the two stops (31, 29) via the at least one dampingspring member (30, 36, 37).
 5. The drill hammer or riveter of claim 4,wherein the first stop (31), toward the guide tube, is formed by aretaining disk, wherein the retaining disk is secured relative to theguide tube (13) by means of a securing ring (34) against axialdisplacement frontward in the direction of a tool holder (20).
 6. Thedrill hammer or riveter of claim 5, wherein on the side of the at leastone damping spring member (30, 36, 37) remote from the tool holder (20),a stop disk, which simultaneously acts as an abutment toward the guidetube for the restoring spring (27), is provided as the second stop (29).7. The drill hammer or riveter of claim 6, wherein in the hammeringposition of the guide tube (13), the stop disk (29) is braced at theback via a bearing ring (28) toward the housing.
 8. The drill hammer orriveter of claim 2, wherein an elastomer element (30) is provided as theat least one damping spring member.
 9. The drill hammer or riveter ofclaim 2, wherein a cup spring assembly (36) is provided as the at leastone damping spring element.
 10. The drill hammer or riveter of claim 2,wherein a helical spring (37) is provided as the at least one dampingspring member.